Transfer of DNS Messages
DNS operates from the Application layer of the TCP/IP reference model. Application protocols such as HTTP interact with DNS for name resolution. For example, if you access the Web site named www.que.com, the application that is using HTTP, which in this case is a Web browser, forwards a query to a computer called the DNS server requesting the corresponding IP address. If the request cannot be resolved locally, a DNS message is created and passed over the network to the DNS server that can answer the queries. DNS relies on the underlying Transport layer protocol to transfer the messages to other computers. The Transport layer protocol that is used by DNS is most commonly UDP. There are a few situations in which TCP ...
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